This invention relates to a cartridge boiler designed for use in multiples in a steam generation plant for power production, cogeneration or steam use. Small and medium size steam generating plants have long been used in factories and institutions for combusting waste products as well as fossil fuels for generation of steam. The generated steam was used primarily for heating and in many instances for processing of manufactured goods or agricultural products. With the design of small efficient steam turbines the combination of a steam generating system with a power production unit has economic merit. However, conventional designs of boilers used for steam heating are customerily low pressure systems ineffective for driving a steam turbine. The requirement for an inexpensive, medium pressure boiler that is safely operable with a variety of often low Btu fuels of inconsistent composition has led to the design of free-expansion tube arrangements and systems using multiple cartridge-like boiler units. While certain prior cartridge boiler designs are advantageous, they pose fabrication complications and do not represent the most effective designs for absolute minimum cost. The boiler system of the present invention is designed to generate steam suitable for electrical power generation from fuels that are of inconsistent composition and vary in thermal potential from 4000 Btu to 20,000 Btu. The boilers are designed primarily for use in multiples enabling flexibility in the design of a plant having a capacity suited for the desired use.
Naturally, however, the boiler as a stand alone unit will find use in situations where maximizing system efficiencies is not a primary goal.